Over the last century, clinicians, which term includes herein certified and licensed medical doctors of all specialties, osteopathic doctors of all specialties, podiatrists, dental doctors of all specialties, chiropractors, veterinarians of all specialties, nurses, and medical imaging technicians, have become dependent on the use of medical devices that assist them in their delivery of patient-centered care. The common function of these devices is to assist and not replace the clinical judgment of the clinician. This fulfills the dictum that best practice is clinical judgment assisted by scientific data and information.
Entering into the era of computer science and sophisticated electronics, clinicians have the opportunity to be supported by data and information in a statistically significant and timely fashion. These advancements have allowed more extensive and useful collection of meaningful data that can be acquired, analyzed, and applied in conjunction with the knowledge and expertise of the clinician.
Medical long-wave infrared (LIR) thermography has been known to be beneficial in the evaluation of thermal heat intensity and gradiency relating to abnormalities of the skin and subcutaneous tissue (SST). Although this technology has expanded to other areas of medical evaluation, the scope of this patent application is limited to the SST abnormalities. These abnormalities include the formation of deep tissue injury (DTI) and subsequent necrosis caused by mechanical stress, infection, auto-immune condition, and vascular flow problems. DTI caused by mechanical stress (pressure, shear and frictional forces) can be separated into three categories. The first category is a high magnitude/short duration mechanical stress represented by traumatic and surgical wounds. The second category is low magnitude/long duration mechanical stress represented by pressure ulcer development, which is also a factor in the development of ischemic and neuropathic wounds. The third category is a combination of categories one and two represented by pressure ulcer formation in the bariatric patient.
The pathophysiologic conditions that occur with DTI and subsequent necrosis of the affected tissue are ischemia, cell distortion, impaired lymphatic drainage, impaired interstitial fluid flow, and reperfusion injury. Category one is dominated by cell distortion and even destruction. Category two is dominated by ischemia. Category three is a combination of cell distortion and ischemia.
Hypoxia causes aerobic metabolism to convert to anaerobic metabolism. This occurrence causes lactic acidosis followed by cell destruction, release of enzymes and lytic reactions. The release of these substances causes additional cell injury and destruction, and initiation of the inflammatory response.
It is very important to recognize that ischemic-reperfusion injury is associated with all of the above mechanical stress induced SST injuries. This condition is caused by a hypoxia induced enzymatic change and the respiratory burst associated with phagocytosis when oxygen returns after an ischemic event. The result of ischemic-reperfusion injury is the formation of oxygen free radicals (hydroxyl, superoxide, and hydrogen peroxide) that cause damage to healthy and already injured cells leading to extension of the original injury
SST injury and subsequent necrosis can also be caused by vascular disorders. Hypoxia can be caused by an arterial occlusion or by venous hypertension. Lymphatic flow or node obstruction can also create vascular induced injury by creating fibrous restriction to venous drainage and subsequent cellular stasis in the capillary system. These disorders are also accentuated by reperfusion injury and oxygen free radical formation.
Infection of the skin (impetigo), subcutaneous tissue (cellulitis), deep tissue (fasciitis), bone (osteomyelitis) and cartilage (chondritis) causes injury and necrosis of the affected tissue. Cells can be injured or destroyed by the microorganism directly, by toxins released by the microorganism and/or the subsequent immune and inflammatory response. These disorders are also accentuated by reperfusion injury and oxygen free radical formation.
Auto-immune morbidities of the skeletal joints (rheumatoid arthritis), subcutaneous tissue (tendonitis, myelitis, dermatitis) and blood vessels (vasculitis) cause similar dysfunction and necrosis of the tissue being affected by the hypersensitivity reactions on the targeted cells and the subsequent inflammatory response. Again, these conditions are accentuated by reperfusion and oxygen free radical formation.
The common event that addresses all of the above SST injuries is the inflammatory response. This response has two stages. The first stage is vascular and the second is cellular. The initial vascular response is vasoconstriction that will last a short time. The constriction causes decrease blood flow to the area of injury. The decrease in blood flow causes vascular “pooling” of blood (passive congestion) in the proximal arterial vasculature in the region of injury and intravascular cellular stasis occurs along with coagulation.
The second vascular response is extensive vasodilation of the blood vessels in the area of necrosis. This dilation along with the “pooled” proximal blood causes increased blood flow with high perfusion pressure into the area of injury. This high pressure flow can cause damage to endothelial cells. Leakage of plasma, protein, and intravascular cells causes more cellular stasis in the capillaries (micro-thrombotic event) and hemorrhage into the area of injury. When the perivascular collagen is injured, intravascular and extravascular coagulation occurs. The rupture of the mast cells causes release of histamine that increases the vascular dilation and the size of the junctions between the endothelial cells. This is the beginning of the cellular phase. More serum and cells (mainly neutrophils) enter into the area of the mixture of injured and destroyed cells by the mechanism of marginalization, emigration (diapedesis) and the chemotaxic recruitment (chemotaxic gradiency). Stalling of the inflammatory stage can cause the area of necrosis (ring of ischemia) to remain in the inflammatory stage long past the anticipated time of 2-4 days. This continuation of the inflammatory stage leads to delayed resolution of the ischemic necrotic event.
The proliferation stage starts before the inflammatory stage recedes. In this stage angiogenesis occurs along with formation of granulation and collagen deposition. Contraction occurs, and peaks, at 5-15 days post injury.
Re-epithelialization occurs by various processes depending on the depth of injury. Partial thickness wounds can resurface within a few days. Full thickness wounds need granulation tissue to form the base for re-epithelialization to occur. The full thickness wound does not heal by regeneration due to the need for scar tissue to repair the wound. The repaired scarred wound has less vascularity and tensile strength of normal regional uninjured SST. The final stage is remodeling. In this stage the collagen changes from type III to a stronger type I and is rearranged into an organized tissue.
All stages of wound healing require adequate vascularization to prevent ischemia, deliver nutrients, and remove metabolic waste. Following the vascular flow and metabolic activity of a necrotic area is currently monitored by patient assessment and clinical findings of swelling, pain, redness, increased temperature, and loss of function.